[GMR]

I'm about to helicoil head bolt hole (#5 in the tightening procedure) on a first gen 350. Motor is fully assembled except for intake and head on the damaged side. The head bolt has more threads than 1 insert. Do I need to match or exceed the number of threads with multiple inserts? I was going to use red locktite on the insert(s) and let sit for 24 hrs. I've read the 'helicoil' threads on the Engine forum. Is it absolutely necessary to break off the tang on the bottom of the insert? Any other advice you can give me?

 

[ericnova72]

The cylinder head deck face is only about as thick as the helicoil insert is long anyway, the bolt sticks down through it, thats why the tang must be removed. Make sure the tap is dead square to the deck face, using the helicoil tap and a drill press to make a tap guide block out of a scrap piece of steel is the hot ticket.

 

[GMR]

Thanks Eric, I'll get to work on the guide block.

Didn't notice before, but looking closely now I believe there's already a helicoil in this hole and its about 3/8" below the deck surface.

I had originally torqued this bolt to 65 lbs then when I went back to re-torque after engine break-in, it let loose. I can still screw a bolt into it just can't get any torque on it now. Do you think a stud would work? I can't redrill and put in another 7/16 X 14 helicoil right?

 

[ericnova72]

If it won't torque, a stud won't change the fact, the threads aren't solid to the parent metal now. If it's already been helicoiled and it has pulled the threads out of the block again, your only hope of fixing it is a Kingsert or Timesert-- a solid threaded bushing like 9/16" od and 7/16" id.

 

[GMR]

ok, thanks Eric

 

[GMR]

I'm researching the timesert but had a thought. What do you think about screwing in a stud and using JB weld or some form of epoxy to make the stud become one with the block - bad idea?

 

[ericnova72]

I'm researching the timesert but had a thought. What do you think about screwing in a stud and using JB weld or some form of epoxy to make the stud become one with the block - bad idea?

Yes, I don't feel JB is good enough for this. You might try Devcon for steel if you can get some, but it will still be an experiment, not a sure thing. My experience is that this kind of experiment fails a lot more than it works, and then you have to do it again, more expense.

 

[GMR]

ok, thanks again Eric.

 

[streetrodderbn]

can you post a picture? It sounds like the existing helicoil has come loose and screwed down into the block! I had the same issue on a flathead ford, and simply removed the existing helicoil,and installed a new one with locktite red in the correct position!

 

[GMR]

streetrodderbn, thanks for the reply - good tip.

 

[GMR]

Can I update this thread - I was wrong about a pre-existing helicoil. I have installed a helicoil in the stripped hole and in torqueing the head a different hole stripped. I'm thinking I'll helicoil all 17 holes.

I've read different opinions - Some say to use studs with the helicoils but to be honest I don't want to spend that much. Cheapest I can find is $133 at Summit for complete set. Can't find anybody selling individual pieces. Can I expect the helicoils to hold the 65 ft lbs of torque required for the head bolt? Also, are the helicoils are one shot deal - if I ever remove the head again what are the chances of them pulling out/stripping?

I talked to the Timesert technical person - it would cost about $120 for me to Timesert all 17 holes. Since I already bought the helicoil kit from NAPA (made in China) for $34, I'm thinking go with the helicoils for the extra $16 worth of inserts only. I'm also concerned that the Chinese tap in the NAPA kit won't last for 17 holes. I'm thinking I should go ahead and get another 7/16 X 14 STI tap if it's a pretty sure bet the tap in the kit won't last.

What's been your experience, what do you guys think?

 

[ericnova72]

Technically, when speaking of Cast iron and Aluminum, the helicoiled hole is now stronger than it was originally as the OD of the insert is grabbing a larger area and the wire itself is stronger than the parent material. For this reason, the better Aluminum aftermarket heads are often equipped with helicoils right from the manufacturer. I've heard of people doing all the head bolt holes in an SBC without problems. With the inserts locktited in, you should have no problem with head bolts, no need to upgrade to studs unless you were going to tear it down on a regular basis like a professional racer would.

 

[GMR]

Thanks Eric.

 

[PatM]

Hearing about holes stripped out near the top, and remaining threads deeper in the hole. Are your bolts long enough?

P

 

[speedydeedy]

As was said the Helicoiled hole is stronger if installed properly. No need to do them all,only the ones that stripped.Just make sure you don't over torque them.

 

[GMR]

Oh, that's a good thought. Pat, I'm using GM head bolts from Summit part #12495499. Just read the description and it says stock, Edelbrock Performer/RPM Heads kit. I'm using RHS vortec heads RHS12407K1 and they recommend ARP-134-3701 but they also say individual application must be verified. I didn't do that. When I was investigating timeserts I did measure the head bolt hole in the block at 1/2" - which, if I measured correctly, is not long enough to use their recommended insert which is a length of .600. So I need to measure the length of the hole in the head, the compressed head gasket thickness and add 1/2" - yes?

Thanks for the reply speedy.

 

[cobalt327]

The 12495499 bolt set should work just fine w/Vortec heads. They are correct 12-point, flanged type.

Don't worry about the bolts being somewhat longer than your measured stack- the holes are not blind- the bolts extend all the way through the deck and into the coolant. Obviously, they need to extend through the thickness of the deck, so can't be too short.

Remember to use thread sealer to keep the coolant where it belongs .

 

[PatM]

GMR

I only mention this because I've seen it in my own garage. Very humbling. Hold the bolt against the cylinder head (or if the head is off, better yet, stick the bolt through), and you'll know. The bolt length should be about 5/8 greater than the head thickness. If it's 3/8 greater . . that's the problem.

Pat

 

[GMR]

Thanks fellas.

 

[Kevin45]

One thing to remember about Heli-coils and breaking the tangs off......WATCH WHERE THE TANG GOES!!!!! If you are putting a heli-coil in something like a head and it is on the engine, make sure the tang DOES NOT get in the engine or you can do some major damage.
Also if you do not break the tang off and run a bolt in, the bolt will bend the tang down. You can run the bolt in fine but when you go to back the bolt out, the tang will start to bend back and will LOCK THE BOLT. Major thread damage results IF you can get the bolt out.
I've put in thousands of heli-coils over the years and have seen about every type of damage that it can do with bolts.
As far as special tang removers...you don't need them. Get a punch slightly smaller than the inside diameter of the heli-coil and a slight rap with a hammer will break it off.
If you have to remove a heli-coil, they make a heli-coil remover that looks like a flat triangular blade and is sharpened for L.H. turning. Tap this into the heli-coil and if lucky you may be able to remove it. In a pinch, I have used the tang of a file and turned them out with a great success rate. The other way, is to take a very small screwdriver, locate the top thread of the heli-coil, get under it and bend it in towards the center. Then take needle-nose pliers, grab it and either turn it out or pull straight up and it will unwind itself out. Although the latter may do some parent material thread damage depending on what the material is.

Didn't mean to go on but just thought I'd give a little heli-coil info if it is useful to anyone.